A wiring diagram for a 1990 L8000 is found in its maintenancemanual. It can also be found at an auto part store, if the techwill print out the diagram. Share to: Show you the Commercial trailer wiring diagram? Need wiring diagram for 1997 ford ranger radio?. download 1997 ford l series foldout wiring diagram l8000 l9000 lt8000 lt9000 ln7000 ln8000 ln9000 lnt8000 lnt9000 ll9000 ltl9000 1997 ford l series pdf.